Chelating agents, or chelators, constitute a well known type of multifunctional organic compounds that are capable of forming complexes of multivalent metal ions such as, for example, calcium, magnesium, zinc, iron, chromium, and lead. Chelators find use in a variety of commercial applications, for example, photographic processing solutions, to which they can be added to form soluble complexes with metal ions that would otherwise produce undesirable precipitates or sludges.
A well known and widely used chelator is ethylenediaminetetraacetic acid, (HO.sub.2 CCH.sub.2).sub.2 NCH.sub.2 CH.sub.2 N(CH.sub.2 CO.sub.2 H).sub.2, commonly referred to as EDTA, commercially available both as the free acid and as various salts, for example, disodium EDTA, tetrasodium EDTA, dipotassium EDTA, calcium disodium EDTA, etc. Other commercial chelators are the naturally occurring amino acid L-cysteine, HSCH.sub.2 CH(NH.sub.2)CO.sub.2 H, and its acetylated derivative N-acetyl-L-cysteine, HSCH.sub.2 CH(NHCOCH.sub.3)CO.sub.2 H, commonly referred to as NAC.
In addition to their industrial applications, chelators have also been extensively employed therapeutically in the treatment of human subjects. For example, injections of EDTA have been used to remove high levels of toxic lead from the bloodstream of individuals who have been exposed to lead paint. Intravenous injection of chelators has also been employed in the treatment of other medical conditions. For example, U.S. Pat. No. 5,114,974 to Rubin discloses the treatment of atherosclereosis with MgNa.sub.2 EDTA.
Chelation therapy to remove potentially harmful metal ions from the body of an individual is today frequently proposed as a means for gaining and maintaining good health and avoiding surgery for heart disease. Although chelation therapy of human patients is most commonly carried out by intravenous injection, oral chelation therapy is also well known. For example, U.S. Pat. No. 5,080,906 to Carenzi et al. discloses a method and composition for oral administration of N-acetylcysteine (NAC).
Various formulations containing one or more chelators for oral administration are commercially available. Typically, these formulations contain a low dosage of chelators, along with a mixture of other purportedly beneficial ingredients. The list of ingredients for one such product, Life Glow Plus.TM. from Vibrant Life contains, per capsule, 25 mg disodium dihydrate EDTA, 15 mg L-cysteine, and 15 mg NAC, and specified amounts of 48 additional substances, including other amino acids, vitamins, minerals, herbs, glandular substances, and "special items." The recommended daily dosage of Life Glow Plus.TM. is 20 capsules.
Another available oral chelation product is Kelation Plus.RTM. from Kelation Plus International, Jacksonville Fla., a powder packaged in individual daily servings and said to contain 26 pharmaceutical grade vitamins, minerals, amino acids, and glandulars. The list of 26 ingredients, all in unspecified amounts, for Kelation Plus.RTM. includes L-cysteine. A footnote to the ingredients list states: "EDTA used as a preservative."
There remains a need for a convenient, orally administered pharmaceutical composition that contains an effective dosage of chelators without included extraneous ingredients that may impair their effectiveness. This need is met by the present invention.